<!DOCTYPE html>
<title>Fallback to a whitespace-only string should not crash</title>
<link rel="author" title="Steinar H. Gunderson" href="mailto:sesse@chromium.org">
<link rel="help" href="https://crbug.com/1476811">
<style>
  #t1 {--a:var(--b,var(--c,) );}
</style>
<div id="t1">Test passes if it does not crash.</div>
